1. Field of the Invention
This invention relates to a spark plug insulator and a method of sintering the same for use in an internal combustion engine.
2. Description of Prior Art
In a spark plug insulator for an internal combustion engine, a nitride-based sintered ceramic body has been employed since the sintered ceramic body has good thermal conductivity while maintaining good electrical insulation.
Taking Japanese Patent Publication No. 46634/1980 as one example of this type of insulator, an oxide of element selected from IIIA group of periodic table, silicate-based compounds and metallic oxides are sintered with aluminum nitride powder as a main component.
The insulator thus sintered, however, decreases its electrical insulation (less than 5 M.OMEGA.) when exposed to high ambient temperature so as to occur electrical leakage, and thus leading to misfire when high voltage is applied across a center electrode and an outer electrode.
Therefore, it is an object of the invention to provide a spark plug insulator which is capable of maintaining an elevated insulation property at high ambient temperature with good thermal conductivity, thus preventing electrical leakage to protect against misfire, and contributing to an extended service life.